The present invention relates to a new and improved fastener which is utilized to interconnect two or more members and to seal the connection between the members.
Relatively light gauge sheet metal panels are commonly connected to building structures to provide a covering which is both aesthetically pleasing and protective of the outside of the building. In order to prevent leakage of water and other substances between the panels and the building, any connections between the panels and the building must be sealed so as to be weather tight. Since the panels have a relatively long service life, for example, 20 years, it is important that a durable seal be provided between the fastener and the panel. Although a fastener constructed in accordance with the present invention can advantageously be utilized to connect sheet metal panels with the outside of a building, it is contemplated that the fastener could be utilized for other purposes, for example to connect light guage sheet metal panels to each other.
In addition to providing a weather tight seal, it is important that a fastener which is used with light gauge sheet metal panels be effective to prevent the panels from being pulled off over the head of the fastener. Since the sheet metal panels are relatively thin, the forces transmitted between the sheet metal and the fastener should be distributed over as large an area as possible to prevent the panel from rupturing or ripping and being pulled off over the head of the fastener.
In addition to the functional requirements that the fastener provide a weather tight seal and distribute forces between the panel and the fastener in such a manner as to prevent pulling off of the panel, it is important that the fastener does not detract from the overall appearance of the outside of the building. To prevent the fastener from detracting from the overall appearance of the outside of the building, the head of the fastener should either match or compliment the color of the panel.
In order to satisfy these diverse requirements, a known fastener has been provided with a plastic outer head or covering in the manner disclosed in U.S. Pat. Nos. 3,134,290 and 3,557,654. Although the fasteners disclosed in these patents are generally satisfactory in connecting panels to the outside of a building, it is believed that the fasteners could be improved to provide a better sealing action and to minimize any possible tendency for pull off of the sheet metal panels over the heads of the fasteners.
In still another effort to provide a fastener to secure a sheet metal plane to the outside of a building, the head of a screw has been provided with a flexible cap of rubber or plastic material which is snapped over the head of the screw in the manner disclosed in U.S. Pat. No. 3,885,492. Since the material of the cap is highly flexible, it is believed that the material of the cap would not be nearly stiff enough to provide a firm seal which would last for the life of the panel. In addition, it is believed that the fastener disclosed in this patent would tend to be susceptible to pull off of the panel since the head of the fastener is provided with a shoulder which engages the panel radially inwardly of the location where the cap seals against the panel. This would tend to concentrate the forces transmitted between the panel and the head of the screw.